Abstract：In order to research the relationship between macro-expansion process and micro-evolution of water-rich slate，the expansion rate test under lateral restraint and the expansion force test under constant volume condition of slate taken from Zhuxi county，Hubei province，were performed to investigate macro swelling deformation of slate. The types of sample minerals were determined by X-ray diffraction(XRD)，the micro- structure of samples after water absorption was observed by scanning electron microscope(SEM) for investigate the internal factors of the expansion of slate after water absorption and the evolution law of the micro-structure，and the T2 spectrum distribution of slate was obtained by NMR for studying the micro-mechanism of mud expansion process of slate. The results show that under the rich-water environment，the expansion rate of slate increases rapidly in the early stage，then tenderly and tends to be stable，while the expansion force shows a slightly decreasing process after quickly increasing up to the maximum. With the prolongation of soaking time，the content of clay minerals in slate increases and the solution tends to be weak alkaline as a whole. The T2 spectrum of natural slate shows double peaks and mainly consists of small pores. After water immersion，the T2 spectrum shows three peaks and the internal macro-pores appear. The total pore volume increases first and then decreases with a maximum value at 2 h of immersion. After water absorption，mineral particles of slate begin to expand，resulting in the increases of the particle volume and the contact force between particles，and consequently，stress and strain tensors increase macroscopically，which explains the internal causes of expansion deformation and expansion force of slate. The slight dissolution of clay minerals makes the expansive stress decrease slightly，which explains the phenomenon of the slight drop of the expansive stress after reaching the maximum. This study can provide a theoretical support for the study of swelling mechanisms of expansive rock.
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2020, Vol. 39 
